1. Field of the Invention
This invention relates to gas moving mechanisms in general and more particularly to an impeller assembly for use in a blower mechanism.
2. Description of the Prior Art
Many structures have been devised for moving gaseous substances, such as air and other blowable materials, such as grain, with a specific type of such structure, commonly referred to as a centrifugal blower, being in wide spread use in, for example, central heating systems, central air conditioning systems, evaporative air cooling systems, and the like.
Although centrifugal blowers differ in structural details, they basically include a scroll-like shaped blower housing having an inlet opening formed in each of the opposite sidewalls thereof so as to be in axial alignment with each other, and having a centrifugal outlet opening. A bearing is carried centrally in each of the axial inlet openings on suitable struts and an axle Shaft is rotatably carried in those bearings. A blower wheel is mounted fast on the axle shaft for rotation therewith, with such an assembly constituting what is hereinafter referred to as an impeller assembly. Rotatable driving of the impeller assembly draws air, or other blowable material, into the blower housing through the axial inlets and discharges it under pressure through the centrifugal outlet.
Various means have been employed for rotatably driving the impeller assembly with the most common method being an electric motor mounted on the exterior of the blower housing, with a drive pulley carried on the motor's output shaft. A relatively large driven pulley is mounted fast on one end of the axle shaft and a V-shaped belt is employed to transmit rotary motion from the drive pulley to the driven pulley. Such a drive system places the driven pulley coaxial with one of the inlet openings of the blower housing immediately outwardly of that opening.
Such positioning of the driven axle pulley places its peripheral rim right in the high velocity flow path into the blower housing which results in a flow restricting turbulence, and in many instances, the belts which drive the pulleys will deteriorate rather rapidly due to the damaging effects of the inlet flow to the blower housing. Also, drive pulleys employed in this manner are relatively expensive.
To overcome these problems, several attempts have been made to fabricate a blower wheel with a pulley formed integrally on the periphery of the wheel itself. This concept has several advantages over the above described separate drive pulley carried on the axle shaft, such as relocation of the drive belt so that it is no longer directly subjected to the deteriorating effects of the blower materials moving into the blower housing. By using a driven pulley which is integral with the blower wheel, the flow restricting turbulence of the separate pulley mounted in the inlet opening of the blower housing is, of course, completely eliminated.
Among the most important advantages of an impeller assembly having a pulley on the periphery of the blower wheel, is that such a pulley is equal, or at least very close, in diameter to the blower wheel, and thus is considerably larger, in most cases, than the practical size limitations of the separate axle mounted pulley. The larger diameter of the pulley provided on the periphery of the blower wheel allows the use of a higher speed motor which inherently runs cooler and is less expensive than slower running motors.
This integral pulley/blower wheel concept has not, however, been commercially accepted due to the necessity of changing the traditional methods of fabricating blower wheels, tooling costs and the like.
A particular prior art patent disclosing a pulley structure as being demountably attached to the periphery of a blower wheel was issued on Nov. 14, 1972, as U.S. Pat. No. 3,702,741, to Adam D. Goettl. Briefly, this patent discloses an especially molded, or otherwise formed, elongated strip of resilient material which is configured with a V-shaped groove extending along its top surface, and a wheel rim gripping formed on each of its opposite sides. The strip is cut to the desired length and its opposite ends brought into abutting engagement to form the strip into a hoop-like pulley structure. In a first embodiment, the hoop-like pulley is placed between juxtaposed rims of a pair of blower wheels which are mounted in a coaxial side-by-side relationship on the axle shaft. In this embodiment the hoop-like pulley is held in this position by the clamping effect of the juxtaposed wheels and by a plurality of radially disposed clip fasteners which hold the wheel rims in the proper clamping position. In a second embodiment, the hoop-like pulley is placed so that one side edge thereof is in engagement with the rim of a single blower wheel. An endless support ring is positioned on the other side edge of the hoop-like pulley, and a plurality of radially disposed bolts are employed to secure the support ring and the hoop-like pulley structure to the rim of the blower wheel.
Like the hereinbefore discussed integral pulley/blower wheel structure, the demountable pulley/blower wheel configuration suggested by the hereinbefore referenced U.S. patent has not achieved commercial acceptance. Although converting from the existing separate axle mounted pulley technology to the demountable hoop-like pulley would not be as difficult and as expensive as converting to the integral pulley concept, the cost for the tooling involved in fabricating the special elongated resilient strips used to form the demountable hoop-like pulley is quite high. This tooling cost in conjunction with assembly time has made industry reluctant to change from its long used technology.
In addition to this cost related drawback, the material of which the demountable pulley was made needed to be resilient to allow it to be shaped into the desired hoop-like configuration and to allow it to conform to the blower wheel rim, or rims. This resilient material, while being beneficial in those respects, has some drawbacks. First, such material is deflectable and the forces exerted thereon by the drive belt tend to deform it by spreading the sides of the V-shaped groove and the like. Secondly, the wear characteristics of such material is questionable and thirdly, it is virtually impossible to hold the abutting ends in a smooth curved configuration and this results in high wear point.
In addition to the above, another problem exists which relates to impeller assemblies, that is, the blower wheels and the axle shafts upon which they are carried. In many cases, the blowable materials moved by centrifugal blowers presents a hostile environment, which significantly shortens the useful life of the centrifugal blowers per se, and oftentimes necessitates premature component replacement.
An outstanding example of this exists in the centrifugal blowers utilized in evaporative air cooling systems. The air handled by the centrifugal blowers in such systems is heavily ladened with free moisture, i.e., that which is not evaporated into the air. This, of course, is condusive to rust and corrosion. In most cases, the moisture is added to the air from a water supply having a high mineral salt content and this contributes significantly to the rust and corrosion problems.
For this reason, the blower wheels and the axle shafts of centrifugal blowers used in evaporative air cooling devices are among the components which are plagued by premature failures.
What occurs is that the blower wheels become rusted fast on the axle shafts and when this happens, it becomes extremely difficult, and sometimes impossible, to remove those components from the blower housing. The need for such removal arises for example, when badly rusted axle shafts and damaged bearings need to be replaced, and in many instances, a reusable blower wheel will be damaged during such removal.
Therefore, a need exists for a new and improved impeller assembly which overcomes some of the problems and shortcomings of the prior art.